public class Computer {
    public void powerOn(){
        System.out.println("打开笔记本");
    }
    public void useDevice(USB usb){
        usb.openDevice();
    }public void closeDevice(USB usb){
        usb.closeDevice();
    }
    public void powerOff(){
        System.out.println("关闭笔记本");
    }
}
